Histopathology of 30 non-operated acoustic schwannomas.

Thirty of 1720 temporal bones from the Wittmaack's Collection contain nonoperated acoustic neuromas, 22 of them large tumors. Histologically, each tumor has to be considered as an individual. Most of the tumors show a mixture of Antoni type A and B. Tumor vascularization is pronounced in half the cases. Vessels of the internal acoustic meatus are found in all cases. Protein contents of the perilymphatic spaces is medium to pronounced in 23 of 30 cases in comparison to the small protein contents of the healthy side. Ganglion geniculi is invaded in 11 cases (9 von Recklinghausen's disease), Ganglion Scarpae in 26 cases (9 von Recklinghausen's disease), and Ganglion spirale in 9 cases (7 von Recklinghausen's disease). Cochlear and vestibular nerve fibers within the internal auditory meatus were affected by the tumor in 28 of 30 cases, the facial nerve only in 11 cases, among them 9 cases of von Recklinghausen's disease. Twenty-six of 30 schwannomas have a portion within the cribriform area of the cochlea fundus, which explains the limitation to radical tumor surgery without damage of the cochlear nerve. These histological findings explain the site of damage of hearing to expand between the cochlea to the auditory brain stem nuclei, and support the audiological experience that a correlation of "acoustic neuroma" and "retrocochlear lesion" is often not correct.